KR20040032172A - ranging processing circuit at passive optical network by synchronous transfer mode - Google Patents

Abstract

PURPOSE: A ranging processing circuit in an ATM PON(Passive Optical Network) is provided to implement a function of measuring a distance through pre-assigned equalization delay measurement in an ATM PON by using a hardware method, thereby minimizing communication stop time in accordance with distance measurement. CONSTITUTION: A data processor(101) converts source data into byte-unit data, and outputs the byte-unit data. A transmission counter(102) inputs the first clock signals to count, and generates a frame synchronous signal for frame recognition. A reception counter(201) inputs the frame synchronous signal to reset, and counts the second clock signals produced by double-multiplying the first clock signals. A PLOAM(Physical Layer Operations Administration and Maintenance) cell processor(103) requests a response in accordance with ranging approval of an ONU(Optical Network Unit) based on a counting value of the transmission counter(102), and outputs a ranging start signal and PLOAM data. A data transmitter(104) transmits the data outputted from the data processor(101) to the ONU as parallel data. A distance measurer(202) inputs the counting value and the second clock signals, counts from a moment when the ranging start signal is inputted to a moment when a response signal is inputted, and transmits a counted value to the PLOAM cell processor(103).

Description

Ranging processing circuit at passive optical network by synchronous transfer mode

The present invention relates to distance measurement for pre-assigned equalization delay measurements in passive optical networks (PONs) using asynchronous transfer mode (ATM). In order to solve the problem of window establishment in the proposed method of distance measurement, it is an asynchronous type that minimizes communication stop time due to distance measurement by implementing in hardware in order to solve the problem of opening window. A ranging processing circuit in a passive optical subscriber network in a transmission mode.

In general, communication networks around the world have been developed into three types: core network, subscriber network, and access network. Recently, as the subscriber's demand for data communication as well as the corporate subscriber's communication demand has exploded, research into a communication system capable of supporting broadband and various services in a subscriber access network has been actively conducted.

Therefore, optical communication, which has been limited to core networks between stations, has been installed, installed and used down to subscriber access networks. The ultimate goal of the subscriber access network is to support optical bandwidth services by providing an optical cable to the home. However, in the subscriber network, since the price is relatively sensitive, the configuration of the low price system is most important. Therefore, in the subscriber access network, the researches to construct the passive optical subscriber network using only passive optical devices, which are relatively low in maintenance and installation cost, have been continuously conducted.

The subscriber access network should be able to support bandwidth from low data rate to high data rate in order to satisfy various user's needs, and should be able to guarantee various quality of service (QoS). Thus, asynchronous transfer mode (ATM) technology has been associated with passive optical device network technology, and asynchronous transfer mode-passive optical subscriber network technology has emerged.

The asynchronous delivery mode-passive optical subscriber network technique described above is generally implemented as shown in FIG. 1, which is attached to an optical line termination (OLT) 11 and an optical distribution network. Network (ODN) 12 and Optical Network Unit (ONU) (13). The OLT 11 communicates with N ONUs (N = 64 maximum) 13 via two-way optical fiber transmission paths.

The OLT 11 transmits information to the ODN 12 through a branched shared fiber connection, and the ODN 12 transmits information from the OLT 11 through N optical fiber links. The N ONUs 13 are transmitted in broadcast form. The ONUs 13 transmit information to the OLT 11 in a time division multiple access (TDMA) manner in an upstream direction.

2 shows a frame structure transmitted and received in this PON structure. FIG. 2A illustrates a downward frame structure, and FIG. 2B illustrates an upward frame structure. As illustrated in (a) of FIG. 2, two frame structures, 155.520 Mbps and 622.08 Mbps, may be applied to the downlink frame structure according to the downlink transmission rate. The downlink frame structure consists of consecutive time slots, each time slot being filled with 53 octets of ATM cells or PLOAM (physical layer operations administration and maintenance) cells. Since a PLOAM cell is inserted every 28 timeslots, the PLOAM cell slot includes two PLOAM cell slots in the case of a 155.520 Mbps downlink frame, which consists of 56 time slots. The 622.08 Mbps downlink frame includes eight PLOAM cell slots, all consisting of 224 time slots with 216 ATM cell slots.

The uplink frame consists of a total of 53 time slots consisting of 56 bytes, and each time slot is allocated to one of a PLOAM cell, an ATM cell, and a divided slot under the control of an OLT. Each time slot includes a three-byte overhead containing information such as guard time, preamble, and delimiter. The payload information of the downstream PLOAM cell for the OAM 48 octets consists of a message for transporting uplink time slot grant and maintenance information, the upstream PLOAM cell is a message And optical power control information

The asynchronous delivery mode-passive optical subscriber network technology described above is being standardized in 983.1 and 983.2 of ITU-T / FSAN, which are standards of the International Organization for Standardization, to support various multimedia services at low cost.

Passive optical subscriber network can be composed of ring, star, and tree type, and it is recommended to have tree type, and time division multiple access method is smoothly performed in optical distribution network. To this end, it is necessary for the OLT to measure the distance of each optical subscriber network unit (ONU) and allocate equalization delays so that the optical subscriber network units can be virtually in the same position. This process is called distance measurement.

As described above, during the distance measurement, the telephone station side optical termination device takes action on all the optical subscriber network units so that the existing optical subscriber network units do not communicate temporarily.

The time when this communication is stopped is called a window. The size of this window is caused by the ambiguity of the distance between the optical subscriber network unit and the telephone-end optical terminator, and in the standard, the ambiguity of the position is 20 km, since the optical subscriber network unit can be anywhere within about 20 km, There is a communication stop time of over 73 cells (about 21 msec) per delay measurement.

This adversely affects the quality of service. The standard ITU-T G .983.1 introduces only the concept of ranging as shown in Figure 3, but does not define anything else. Since the conventional distance measuring method is generally made by software, the length of the ranging window is long, resulting in a problem of low consumer reliability.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems relates to distance measurement for line allocation equalization delay measurement in a passive optical subscriber network using asynchronous transmission mode. In particular, a window generated in the method of distance measurement proposed in standardization In order to solve the problem, the ranging processing circuit is provided in the passive optical subscriber network of the asynchronous transmission mode to minimize the communication down time according to the distance measurement by implementing the hardware in the hardware. There is.

1 is a general ATM-PON block diagram,

2 is a structural diagram of a PON frame

3 is an example of the concept of lasing mentioned in the recommended rule

4 is an exemplary block diagram of a ranging processing circuit in a passive optical subscriber network in an asynchronous transmission mode according to the present invention.

5 is an exemplary waveform diagram illustrating a counter-synchronous matching process of the transmission and reception counter of FIG. 4.

6 is an exemplary waveform diagram illustrating a process of ranging processing performed by a ranging processing circuit in a passive optical subscriber network in an asynchronous transmission mode according to the present invention;

In order to achieve the above object, an aspect of the present invention provides an optical line termination device for passive optical subscriber network control in asynchronous transmission mode for controlling communication between an external asynchronous transmission mode layer processor and a plurality of optical network units. A data processor converting and outputting arbitrary source data into data in a unit of a byte to enable transmission; A transmission counter unit receiving and counting a first clock signal to synchronize transmission data in a transmission mode, and generating a frame synchronization signal for frame recognition for data transmission; A reception counter unit for receiving and resetting a frame synchronization signal generated by the transmission counter unit and counting a second clock signal obtained by multiplying the first clock signal by two; PLOAM which requests the response according to the ranging approval based on the counting value output from the transmission counter unit in synchronization with the first clock signal and outputs a ranging start signal and PLOAM data according to the approval request. A cell processor; A data transmitter which transmits the transmission data output from the data processor to the optical network unit as parallel data in synchronization with the first clock signal based on the PLOAM data output from the PLOAM cell processor; And a response signal according to the ranging approval from the optical network unit from a time point when the ranging start signal outputted from the PLOAM cell processor is input based on the counting value and the second clock signal output from the reception counter unit. And a distance measuring unit for counting up to a time point at which P is input and transmitting the value to the PLOAM cell processing unit as a value for transmission delay for each optical network unit.

As an additional feature of the present invention for achieving the above object, the transmission counter unit, when the rate of the downlink data is 622MHz, 53 bytes per cell, 28 cells per PLOAM cell, 78MHz clock for transmission of 8 PLOAM cells per frame It consists of a 14-bit byte counter that operates as an 8x28x53 counter using.

As another additional feature of the present invention for achieving the above object, the reception counter unit is a 15-bit byte counter that operates as a 53x56x8 counter using a 155MHz clock as one frame is composed of 53 cells of 56 bytes. It is composed.

The above object and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

4 is an exemplary block diagram of a ranging processing circuit in a passive optical subscriber network in an asynchronous transmission mode according to the present invention, which is largely divided into a transmitter and a receiver. The transmitter is capable of transmitting any source data to be transmitted. The data processing unit 101 converts and outputs data in byte units, and receives and counts a count value TCNT and a frame by receiving and counting a transmission synchronization clock 78CLK having a frequency of 77.76 MHz to synchronize transmission data in a transmission mode. Transmit counter unit 102 for outputting a frame synchronization signal (FP) for receiving, the counting value (TCNT) and the transmit synchronization clock (78CLK) output from the transmit counter unit 102 is received according to the operation of each physical layer The PLOA in synchronization with the PLOAM cell processing unit 103 for outputting PLOAM data PLOAMD in byte units for maintenance and the transmission synchronization clock 78CLK. Data transmission unit for receiving the PLOAM data (PLOAMD) output from the M cell processing unit 103 and transmits the transmission data PD output from the data processing unit 101 to the ONU side of the optical network unit in parallel data type ( 104).

At this time, the PLOAM cell processing unit 103 is to recognize the transmission time after the start of the ranging based on the equal delay signal according to the distance delay of the receiver to be described below.

Subsequently, the receiving unit receives the frame synchronizing signal FP generated by the transmitting counter 102 of the transmitting unit and recognizes it as a starting point, and receives the receiving synchronization having a frequency of 155.52 MHz by dividing the transmitting synchronization clock 78CLK of the transmitting unit by two. Receive counter unit 201 that receives and counts clock 155CLK, and outputs the counting value RCNT and receive synchronization clock 155CLK outputted from receiving counter unit 201 based on the optical network unit. To receive the serial data (ONUD) generated from the ONU and receive the ranging start signal (RAN) generated from the PLOAM cell processing unit 103 of the transmitter to transmit delay for each of the N optical network units (ONU). It is composed of a distance measuring unit 202 for transmitting the value (EDCNT) to the PLOAM cell processing unit 103 side of the transmitter.

The waveforms shown in FIGS. 4 and 5 attached to the operation of the ranging processing circuit in the passive optical subscriber network of the asynchronous transmission mode according to the present invention configured as described above will be described as an example.

5 is a diagram illustrating a main waveform for explaining the counter-synchronous matching process of the transmission and reception counter of FIG. 4, and FIG. 6 is a ranging through a ranging processing circuit in a passive optical subscriber network in an asynchronous transmission mode according to the present invention. It is an example waveform diagram for demonstrating the process in which a process is performed.

First of all, the transmission counter 102 and the reception counter 201 are generally downlink data rate of 622 MHz so that 53 bytes per cell, 28 cells per PLOAM cell, and 8 PLOAM cells per frame are dropped. Should go Thus, the transmission counter section 102 is composed of a 14-bit byte counter that operates as an 8x28x53 counter using a 78 MHz clock.

In contrast, the reception counter 201 is composed of a 15-bit byte counter which operates as a 53x56x8 counter using a 155 MHz clock because a frame is composed of 53 cells of 56 bytes.

Accordingly, as shown in FIG. 5, the transmission counter unit 102 generates a frame synchronizing signal FP while counting a clock of 78 CLK. Accordingly, the reception counter unit 201 generates the frame counter signal 201. The counter initialization operation is performed by the reset operation performed by the frame synchronization signal FP generated and input, thereby synchronizing with the transmission counter 102. Thereafter, the reception counter unit 201 counts a clock of 155 CLK.

In addition, the PLOAM cell processing unit 103 outputs a signal, referred to as reference number RAN, to start ranging to the distance measuring unit 202, and the optical network unit ONU, ranging through the GRANT portion inside the PLOAM cell. It sends a ranging grant.

Therefore, the distance measuring unit 202 receiving the ranging start signal RAN receives a counter at the time when data is received, as shown in FIG. Measure the value T. A counting operation calculates an equalization delay value based on the counting value when a response corresponding to a ranging grant of the PLOAM cell processing unit 103 is received from the optical network unit ONU. To be transmitted to the PLOAM cell processing unit 103.

The data processing unit 101 is composed of 53 bytes of cells for downlink data. The data input unit 104 multiplexes the data inputted from the data processing unit 101 and the PLOAM cell processing unit 103 to the optical network unit ONU. Will transmit the data.

In this case, as described above, in the optical network unit (ONU), if data is transmitted after an equal delay received through an acknowledgment message in a PLOAM cell, data transmission is possible while suppressing data collision regardless of distance.

While the invention has been shown and described in connection with specific embodiments thereof, it is well known in the art that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the claims. Anyone who owns it can easily find out.

As described above, the provision of a ranging processing circuit in a passive optical subscriber network in an asynchronous transmission mode according to the present invention provides a hardware implementation for ranging, which is only conceptually mentioned in the standard ITU-T G .983.1. It is possible to provide a reliable processing circuit, and solve the problem that the reliability of the consumer is lowered due to the long length of the ranging window in the prior art.

Claims (1)

In the optical line terminator for passive optical subscriber network control of asynchronous transmission mode for controlling communication between an external asynchronous transmission mode layer processor and a plurality of optical network units: A data processing unit converting and outputting arbitrary source data to be transmitted into data in a byte unit to enable transmission; A transmission counter unit receiving and counting a first clock signal to synchronize transmission data in a transmission mode, and generating a frame synchronization signal for frame recognition for data transmission; A reception counter unit for receiving and resetting a frame synchronization signal generated by the transmission counter unit and counting a second clock signal obtained by multiplying the first clock signal by two; PLOAM which requests the response according to the ranging approval based on the counting value output from the transmission counter unit in synchronization with the first clock signal and outputs a ranging start signal and PLOAM data according to the approval request. A cell processor; A data transmitter which transmits the transmission data output from the data processor to the optical network unit as parallel data in synchronization with the first clock signal based on the PLOAM data output from the PLOAM cell processor; And When the ranging start signal outputted from the PLOAM cell processor is input based on the counting value and the second clock signal output from the reception counter unit, the response signal according to the ranging approval is received from the optical network unit. A lane in the passive optical subscriber network of the asynchronous transmission mode, characterized in that it comprises a distance measuring unit counting up to the input time point and transmitting the value to the PLOAM cell processing unit as a value for transmission delay for each optical network unit. Gong processing circuit.